Two a more power supplies are often connected together in a diode-or arrangement for reliability through redundancy. The power supply providing the lower output voltage in such an arrangement is typically turned off by an error feedback amplifier when that amplifier detects a higher output voltage from another power supply. Various arrangements have been developed to prevent the low output voltage power supply from turning off when there is a small increase in output voltage from another diode-or connected power supply.
U.S. Pat. No. 3,428,820 issued to G. F. Lyon on Feb. 18, 1969 discloses an electro-responsive switching network for a system to be selectively deactivated. U.S. Pat. No. 3,736,491 issued to K. H. Kuster on May 29, 1973 discloses a D.C. to D.C. regulated current fold back power supply which limits output current in an overload state. U.S. Pat. No. 3,808,452 issued to H. F. Hutchinson on Apr. 30, 1974 discloses a power supply system having redundant DC power supplies. However, each of these patents discloses a power supply system which involves complex circuitry for sensing the output of interconnected power supplies.
The present invention provides a novel arrangement for operating diode-or connected power supplies in an active-standby arrangement through use of a novel control circuit which does not require the complex circuitry utilized in the prior art.